Properties of isolates included in the study

  • a NA, not applicable; ND, not determined.

  • b Colistin MIC values were determined by both broth microdilution and strip-based methods, in CA-MH broth and CE-MH broth. False-susceptible isolates that were resistant with the test method (BMD in CE-MH broth) and susceptible with the reference method (BMD in CA-MH broth) are highlighted in gray.

  • c mcr-1-negative, colistin-susceptible isolates.

  • d mcr-1-positive isolates.

  • e Mutation in the mgrB gene involved in colistin resistance.

  • f Mutation in the pmrB gene (D149Y) involved in colistin resistance.

  • g Intrinsically polymyxin-resistant species.